<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<style type="text/css">
	/* 将含有div的第一代span设置为红色，后面的span不动 */
	div>span{
		color:red;
	}
</style>
</head>
<body>
<div>
	<span>一层</span>
	<p><span>二层</span></p>
</div>
</body>
</html>